Hi, Brittany,
first, you can start switching her over now. Mix the alfalfa with timothy pellets for about a week, gradually lowering the percentage of alfalfa in the mix. By the second week she should be changed over completely. You can get some alfalfa cubes as treats for a while if she misses the taste.
I would try some simple veggies, and not too much to get her to start liking them. Once the alfalfa is gone, she may change her mind. I always like romaine, green or red leaf lettuces as base veggies. Also, try mint and parsley. bunnies can develop tastes for things gradually. You can give her carrots and carrot tops if she resists other veggies. Just don’t change it frequently. Try one kind one week, another the next, and stick with any she likes.
I would not risk the outdoor grasses, only because other people’s grasses and seeds that had pesticides can blow into your yard and mix in the mowed pile. Orchard grass, timothy hay, oat hay, etc. are a staple of their diet so you can get it in big bags that will last a while inexpensively once you find her favorite.